Yeah i went powerlvling on trainers. I have a perfect counter for every trainer (that gives a bag). If you deal with all trainers a day you can lvl 2 pets too 25 easy.
(but its a challange still)
In total to get you idea i only got 1 magic battle stone out of 426 Sack of Pet Supplies. (and 2x porcupine)
71 (pets) x 12 bag (a day) = 35.5 days = 426 bags
I only did 12 trainers a day (major pain, and elite 4 are too pain in *** to lvl pets on them)